Mark isInUse per-window

Bug: 22509159
Change-Id: I0ae0f1fa582ee38dcb9f24ca20f0b4d0c57ccb32
diff --git a/libs/hwui/Texture.h b/libs/hwui/Texture.h
index 7227ce0..4bcd96d 100644
--- a/libs/hwui/Texture.h
+++ b/libs/hwui/Texture.h
@@ -97,7 +97,7 @@
      * Whether or not the Texture is marked in use and thus not evictable for
      * the current frame. This is reset at the start of a new frame.
      */
-    bool isInUse = false;
+    void* isInUse = nullptr;
 
 private:
     /**